Problem: $-5a - 7b + 8c - 1 = 2b - c + 4$ Solve for $a$.
Solution: Combine constant terms on the right. $-5a - 7b + 8c - {1} = 2b - c + {4}$ $-5a - 7b + 8c = 2b - c + {5}$ Combine $c$ terms on the right. $-5a - 7b + {8c} = 2b - {c} + 5$ $-5a - 7b = 2b - {9c} + 5$ Combine $b$ terms on the right. $-5a - {7b} = {2b} - 9c + 5$ $-5a = {9b} - 9c + 5$ Isolate $a$ $-{5}a = 9b - 9c + 5$ $a = \dfrac{ 9b - 9c + 5 }{ -{5} }$ Swap the signs so the denominator isn't negative. $a = \dfrac{ -{9}b + {9}c - {5} }{ {5} }$